Hydrogen-bond regulation in organic/aqueous hybrid electrolyte for safe and high-voltage K-ion batteries

Abstract

High reliability and proven ultra-long life make aqueous batteries ideal for grid energy storage. However, the narrow electrochemical stability window (ESW) caused by the high activity of H₂O severely hampers their practical applications. Here, hydrogen-bond (H-bond) regulation is applied using succinonitrile (SCN) to reconstruct the binding state of H₂O molecules, in which the “free H₂O” with strong H-bond network is converted to the “immobilized H₂O” restricted by SCN molecules, thus inhibiting the activity of H₂O. The designed 5.6 m KFSI–SCN–H₂O hybrid electrolyte exhibits an expanded ESW over 4.0 V, particularly with a high anodic limit above 5.1 V, which is the highest among the reported aqueous K-ion electrolytes. Moreover, the electrolyte possesses non-flammability, improved conductivity, and a wider applicable temperature range. As a result, the assembled KVPO₄F||PTCDI full cell exhibits excellent cycling stability over 10 000 cycles with a low capacity decay of 0.0025% per cycle and provides a competitive energy density of about 100 W h kg⁻¹. This work provides insights into how the H-bond regulation strategy inhibits the activity of H₂O in organic/aqueous hybrid electrolytes, offering a promising pathway to achieve higher-energy-density aqueous batteries without compromising safety.